Multiple output multicarrier transmitter and methods for spatial interleaving a plurality of spatial streams

ABSTRACT

A multicarrier transmitter performs bit-interleaving suitable for transmitting more than one spatial stream over a multicarrier communication channel. The multicarrier transmitter may include a bit-grouping shifter to shift QAM symbol-bit groupings of a spatial stream among subcarriers of the multicarrier communication signal, and a bit-position permuter to rotate bits among bit positions within subgroupings of the QAM symbol-bit groupings of the second spatial stream.

TECHNICAL FIELD

Embodiments of the present invention pertain to electroniccommunications. Some embodiments pertain to multicarrier communicationsystems, and some embodiments pertain to wireless local area networks(WLANs).

BACKGROUND

Many wireless communication systems employ an interleaving scheme toreduce errors in transmission. Interleaving, for example, may helpreduce the number of uncorrected error bursts, especially in fadingchannels. Interleaving is generally performed after channel encoding andpermutes bits in a regular or predetermined fashion prior to modulationand transmission. Upon reception and after demodulation, adeinterleaving process is performed to restore the original bitsequence. Some orthogonal frequency division multiplexed (OFDM) systemsuse coding and frequency interleaving to help overcome problemsassociated with transmitting data over frequency-selective (i.e.,fading) channels. Interleaving may exploit this frequency diversity byspreading adjacent bits across the transmission bandwidth.

Some multicarrier transmitters transmit more than one spatial stream onthe same multicarrier communication channel. Conventional interleavingschemes may not provide sufficient bit separation between thesubcarriers of these spatial channels. Conventional interleaving schemesmay also not provide sufficient bit separation between bit positions ofsymbols. Thus there are general needs for multicarrier transmitters andmethods of interleaving suitable for the transmission of more than onespatial stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a multicarrier transmitter in accordancewith some embodiments of the present invention;

FIG. 2 illustrates the operation of a commutator in accordance with someembodiments of the present invention;

FIG. 3 illustrates the operation of a spatial-bit sequencer inaccordance with some embodiments of the present invention;

FIG. 4 illustrates an example output of a block permuter in accordancewith some embodiments of the present invention;

FIGS. 5A and 5B illustrate the operations of bit-grouping shifters andbit-position permuters in accordance with some embodiments of thepresent invention; and

FIG. 6 is a flow chart of a spatial stream transmission procedure inaccordance with some embodiments of the present invention.

DETAILED DESCRIPTION

The following description and the drawings illustrate specificembodiments of the invention sufficiently to enable those skilled in theart to practice them. Other embodiments may incorporate structural,logical, electrical, process, and other changes. Examples merely typifypossible variations. Individual components and functions are optionalunless explicitly required, and the sequence of operations may vary.Portions and features of some embodiments may be included in orsubstituted for those of others. Embodiments of the invention set forthin the claims encompass all available equivalents of those claims.Embodiments of the invention may be referred to, individually orcollectively, herein by the term “invention” merely for convenience andwithout intending to voluntarily limit the scope of this application toany single invention or inventive concept if more than one is in factdisclosed.

FIG. 1 is a block diagram of a multicarrier transmitter in accordancewith some embodiments of the present invention. Multicarrier transmitter100 may transmit two or more spatial streams with antennas 120 frominput bit stream 101. In some embodiments, multicarrier transmitter 100includes scrambler 102 to scramble bits of input bit stream 101 togenerate scrambled bit stream 103. In some embodiments, scrambler 102may generate pseudo-random bits. Multicarrier transmitter 100 alsoincludes commutator 104 to assign bits of bit stream 103 to one of aplurality of data streams 105, and encoders 106 associated with datastreams 105 to receive the assigned bits from commutator 104. Encoders106 may perform an encoding operation on the assigned bits. Multicarriertransmitter 100 also includes spatial-bit sequencer 108 to select groupsof bits from each of data streams 107 to generate two or more spatialstreams 109. Multicarrier transmitter 100 also includes block permuters110 associated with each of the spatial streams to perform a blockinterleaving operation on bits of spatial streams 109 provided byspatial-bit sequencer 108.

In some embodiments, commutator 104 may sequentially assign bits of bitstream 103 to one of data streams 105, and spatial-bit sequencer 108 maysequentially select groups of bits from each of the data streams 107 togenerate up to four or more spatial streams 109, although the scope ofthe invention is not limited in this respect.

The operation of commutator 104 is illustrated in FIG. 2 in which a bitclock operating at a bit rate may select individual bits of bit stream103 and provide each selected bit sequentially to one of encoders 106.In these example embodiments, every fourth bit may be assigned to one ofencoders 106. In some embodiments, because commutator 104 may assignbits of bit stream 103 to more than one encoder 106, the rate at whichan encoder may operate can be reduced. In some embodiments, encoders 106may comprise convolutional encoders and may generate encoded bits. Insome embodiments, encoders 106 may employ error-correcting techniques,although the scope of the invention is not limited in this respect. Eachencoder 106 may generate encoded bits associated with a particular datastream 107. Although FIGS. 1 & 2 illustrate four encoders 106 in whicheach encoder is associated with one of four data streams 107, the scopeof the invention is not limited in this respect.

In some embodiments, spatial-bit sequencer 108 may select groups of fourbits from each data stream 107 to generate more than one of spatialstreams 109. An example of the operation spatial-bit sequencer 108 isillustrated in FIG. 3. In FIG. 3, spatial-bit sequencer 108 may selectbits from encoders 106 at ¼ the bit clock and may provide the selectedbits to permuters 110 at the bit clock rate. In these exampleembodiments, groups of four encoded bits may be selected from each ofencoders 106 and provided individually to permuters 110. For example,spatial-bit sequencer 108 may select four encoded bits from the firstencoder, and may provide the first bit to first permuter 110A, thesecond bit to second permuter 110B, the third bit to third permuter110C, and the fourth bit fourth permuter 110D.

Although FIGS. 1 & 3 illustrates spatial-bit sequencer 108 receivingfour data streams 107 and generating four spatial streams 109, someembodiments of the present invention do not require such a one-to-onecorrespondence between data streams 107 and spatial streams 109. In someembodiments, the number of data streams 107 may differ from the numberof spatial streams 109.

Referring to FIG. 1, multicarrier transmitter 100 also includes one ormore bit-grouping shifters (BGS) 112B-112D to shift symbol-bit groupingsof an associated spatial stream (e.g., spatial streams 111B-111D) amongsubcarriers of a multicarrier communication signal. Multicarriertransmitter 100 also includes one or more bit-position permuters (BPP)114B-114D to rotate bits among bit positions within subgroupings of thesymbol-bit groupings of an associated spatial stream. The operations ofbit-grouping shifters 112B-112D and bit-position permuters 114B-114D aredescribed in more detail below.

Multicarrier transmitter 100 also includes mappers 116A-116D associatedwith a spatial stream to map bits from within bit positions to symbols.Mappers 116A-116D may also symbol-modulate the mapped symbol-bitgroupings and may generate symbol-modulated subcarriers 117A-117Dassociated with a spatial stream. Multicarrier transmitter 100 alsoincludes transmission (TX) circuitry 118A-118D associated with eachspatial stream. Each spatial stream may be transmitted by one of aplurality of transmit antennas 120. In these embodiments, one antennamay be used to transmit an associated spatial stream. In someembodiments, the number of antennas may be at least as great as thenumber of spatial streams being transmitted. In some embodiments,transmitter 100 may further comprise a beamformer (not separatelyillustrated) to operate on symbol-modulated subcarriers representing thespatial streams to generate combined signals for transmission bytransmit antennas 120.

Transmission circuitry 118A-118D may include, among other things,inverse fast Fourier transformation (IFFT) circuitry to generatetime-domain samples from the frequency domain samples comprisingsymbol-modulated subcarriers 117A-117D. Transmission circuitry 118A-118Dmay also include analog-to-digital conversion circuitry to generateanalog I and Q signals, and radio-frequency (RF) circuitry to generateRF signals for transmission by an associated one of antennas 120.

FIG. 4 illustrates example output 400 of one of block permuters 110(FIG. 1). This example illustrates a modulation level of 64-QAM in sixbits comprise each symbol (i.e., three I bits and three Q-bits). Theassigned subcarriers of the multicarrier communication channelcorrespond to the different rows. In FIG. 4, the numbers in the tablerefer to a sequence number of the bits of a bit sequence received at theinput of one of block permuters 110 (FIG. 1). At the output of one ofblock permuters 110 (FIG. 1), bits may be provided by row in the orderillustrated. In some embodiments, block permuters 110 (FIG. 1) mayperform a block interleaving operation in accordance with the IEEE802.11a standard referenced below, although the scope of the inventionis not limited in this respect. Other block permuting operations arealso suitable for use by block permuters 110 (FIG. 1). As illustrated inthe example of FIG. 4, sequential bits at the input of one of permuters110 (FIG. 1) are separated by three subcarriers which result from ablock permutation, although the scope of the invention is not limited inthis respect.

FIGS. 5A and 5B illustrate the operations of bit-grouping shifters andbit-position permuters in accordance with some embodiments of thepresent invention. FIG. 5A illustrates bits of first spatial stream 502and FIG. 5B illustrates bits of second spatial stream 522. The values ofthe numbers in FIGS. 5A and 5B correspond to sequential bits from eachof encoders 106 (FIG. 1) where the first digit corresponds to thedecoder number. In this example, bits from four decoders areillustrated. In this example, bit “1001” is a first bit provided by afirst of the decoders, and bit “4097” is a ninety seventh bit providedby the fourth of the decoders.

Each spatial stream 202 and 222 may comprise symbol-bit groupings 508 or528 which comprise in-phase (I) subgroupings 504 and quadrature-phase(Q) subgroupings 506. First spatial stream 502 may correspond to firstspatial stream 111A (FIG. 1) and second spatial stream 522 may refer tosecond spatial stream 111B (FIG. 1). In FIGS. 5A and 5B, each row ofbits may be associated with a subcarrier frequency (e.g., tone) of amulticarrier communication signal. For clarity, only a few of symbol-bitgroupings 508 are 528 are circled. Third spatial stream 111C (FIG. 1)and fourth spatial stream 111D (FIG. 1) may be similar.

Referring to FIGS. 1, 5A and 5B together, in some embodiments,multicarrier transmitter 100 may use two or more antennas 120 fortransmitting at least first and second spatial streams 111A & 111B. Inthese embodiments, first bit-grouping shifter 112B may shift symbol-bitgroupings 528 of second spatial stream 522 among the subcarriers of themulticarrier communication signal. In these embodiments, bit-positionpermuter 114B may rotate bits among bit positions 510-514 within Isubgrouping 504 and may rotate bits among bit positions 516-520 within Qsubgrouping 506 of second spatial stream 522 to generate output bitstream 115B.

In some embodiments, symbol-bit groupings 528 may bequadrature-amplitude-modulation (QAM) bit groupings. In someembodiments, bit-position permuter 114B circularly rotates bits amongpositions within I subgroupings 504 and within Q subgroupings 506.

In some embodiments, the QAM bit groupings may have a predeterminednumber of bits associated therewith. The predetermined number of bitsper QAM bit grouping may range from two-bits per symbol (BPSK) or fourbits per symbol (16-QAM) to eight or more bits per symbol (256-QAM). Insome embodiments, the QAM bit groupings may have a predetermined numberof bits. FIGS. 5A and 5B illustrate a modulation level of 64-QAM, whichcommunicates six bits per symbol, although the scope of the invention isnot limited in this respect. Modulation levels with lower and higherdata communication rates per subcarrier may also be used.

In some embodiments, the number of subcarriers that bit-groupingshifters 112B-112D shifts the QAM bit groupings may be based on aspatial stream index. The spatial stream index may be different for eachspatial stream. For example, first spatial stream 111A may have an indexof zero, the second spatial stream 111B may have an index of 1, thirdspatial stream 111C may have an index of two, and fourth spatial stream111D may have an index of three. The spatial stream index may be used bybit-grouping shifters 112B-112D and bit-position permuters 114B-114D toprovide differing amounts of bit shifting and bit position rotating foreach spatial stream as described below. In some embodiments, the spatialstream index may be arbitrarily assigned.

The number of bit positions within I subgroupings 504 and within Qsubgroupings 506 of QAM symbol-bit groupings 528 that the bits arecircularly rotated by bit-position permuters 114B-114D may also based onthe spatial stream index. Although multicarrier transmitter 100 isillustrated as having bit-grouping shifters 112B-112D in a signalprocessing path prior to bit-position permuters 114B-114D, in some otherembodiments, the order of these operations may be interchanged.

In some embodiments, first spatial stream 111A may have an index of zeroand therefore the QAM bit groupings are not shifted by a bit-groupingshifter and bits are not rotated among bit positions within I and Qsubgroupings by a bit-position permuter. In these embodiments, secondspatial stream 111B may have an index of one and therefore the QAM bitgroupings may be shifted by three subcarriers (e.g., three times theindex) by bit-grouping shifter 112B, and the bits within the Isubgroupings 504 and within Q subgroupings 506 may be rotated by one bitposition (e.g., one times the index) by bit-position permuter 114B. Inthese embodiments, third spatial stream 111C may have an index of twoand therefore the QAM bit groupings may be shifted by six subcarriers(e.g., three times the index) by bit-grouping shifter 112C, and the bitswithin the I subgroupings and within the Q subgroupings may be rotatedby two bit positions (e.g., one times the index) by bit-positionpermuter 114C. In these embodiments, fourth spatial stream 111D may havean index of three and therefore the QAM bit groupings may be shifted bynine subcarriers (e.g., three times the index) by bit-grouping shifter112D, and the bits within the I subgroupings and within Q subgroupingsmay be rotated by three bit positions (e.g., one times the index) bybit-position permuter 114D. In this way, QAM symbol shifting andbit-position rotation may be performed on all spatial streams but one(e.g., the first one).

Although FIG. 5 illustrates an example for 64-QAM with four spatialstreams in which the QAM groupings are shifted a number of subcarriersbased on a factor of three times the spatial stream index, the scope ofthe invention is not limited in this respect. Different amounts ofshifting may be performed depending on the type of permuting performedby block permuters 110 to help provide a maximal subcarrier separationbetween adjacent bit and near adjacent bits at the output of thebit-grouping shifters.

In some embodiments, first bit-position permuter 114B may circularlyrotate bits among bit-positions with I subgroupings and within Qsubgroupings of each of QAM bit groupings 528. Each of QAM bit groupings528 may be associated with one subcarrier of the multicarriercommunication signal, and first bit-grouping shifter 112B shifts QAM bitgroupings 528 by a plurality of subcarriers of the multicarriercommunication signal.

In some embodiments, bit-position permuter 114B may rotate bits of Isubgroupings 504 in columns 510, 512 and 514 left by one column (i.e.,one bit position) so that bits originally in column 510 reside in column514, bits originally in column 512 reside in column 510, and bitsoriginally in column 514 now reside in column 512. Similarlybit-position permuter 114B may rotate bits of Q subgroupings 506 incolumns 516, 518 and 512 left by one column (i.e., one bit position) sothat bits originally in column 516 reside in column 520, bits originallyin column 518 reside in column 516, and bits originally in column 520now reside in column 516. The shift may be performed in eitherdirection. In the case of a three bit position shift, the bits result intheir original position because there are three bits per I or Qsubgrouping as illustrated, however, the scope of the invention is notlimited in this respect. In some other embodiments, the I and Qsubgroupings may comprise a higher number of bits per symbol grouping.

In some embodiments, first QAM mapper 116A may include a first symbolmodulator to symbol-modulate QAM symbol-bit groupings of first spatialstream 111A to generate a first plurality of symbol-modulatedsubcarriers 117A. Second QAM mapper 116B may include a second symbolmodulator to symbol-modulate the QAM symbol-bit groupings of the secondspatial stream 115B after operation of first bit-grouping shifter 112Band first bit-position permuter 114B to generate a second plurality ofsymbol-modulated subcarriers 117B. The first plurality ofsymbol-modulated subcarriers 117A may comprise a first orthogonalfrequency division multiplexed (OFDM) symbol for subsequent transmissionby first antenna 120A, and the second plurality of symbol-modulatedsubcarriers 117B may comprise a second OFDM symbol for subsequenttransmission by second antenna 120B.

In some embodiments, first block permuter 110A may perform a blockinterleaving operation on bits 109 associated with the first spatialstream. Second block permuter 110B may perform the block interleavingoperation on bits associated with the second spatial stream prioroperation of bit-grouping shifter 112B and bit-position permuter 114B.

In some embodiments, first bit-grouping shifter 112B may shift eachsymbol-bit grouping 528 of second spatial stream 522 by a predeterminednumber of subcarriers based on a spatial stream index of the secondspatial stream, and first bit-position permuter 114B may rotate bitswithin the I subgroupings and within the Q subgroupings of symbol-bitgroupings 528 of second spatial stream 522 by a predetermined number ofbit positions for all of the subcarriers of the multicarriercommunication signal. The predetermined number bit positions may bebased on the spatial stream index of the second spatial stream. In someembodiments, first bit-grouping shifter 112B may shift each symbol-bitgrouping 528 of second spatial stream 522 by three subcarriers, andfirst bit-position permuter 114B may rotate bits within I subgroupings504 and within Q subgroupings 506 of the symbol-bit groupings 528 ofsecond spatial stream 522 by one bit position, although the scope of theinvention is not limited in this respect.

In some embodiments that transmit more than two spatial streams,multicarrier transmitter 100 also comprises second bit-grouping shifter112C to shift symbol-bit groupings of third spatial stream 111C by apredetermined number of subcarriers based on a spatial stream index ofthird spatial stream 111C. Multicarrier transmitter 100 may also includesecond bit-position permuter 114C to rotate bits within the Isubgroupings and within the Q subgroupings of the symbol-bit groupingsof third spatial stream 111C by a predetermined number of bit-positionsfor all of the subcarriers of the multicarrier communication signal. Thepredetermined number of bit positions may be based on the spatial streamindex of third spatial stream 111C. In these embodiments, multicarriertransmitter 100 may also include third QAM mapper 116C tosymbol-modulate the symbol-bit groupings of third spatial stream 115Cafter operation of second bit-grouping shifter 112C and secondbit-position permuter 114C to generate a third plurality ofsymbol-modulated subcarriers 117C. The third plurality ofsymbol-modulated subcarriers 117C may comprise a third orthogonalfrequency division multiplexed symbol for subsequent transmission bythird antenna 120C.

In some embodiments, second bit-grouping shifter 112C shifts each QAMsymbol-bit grouping of third spatial stream 111C by six subcarriers. Inthese embodiments, second bit-position permuter 114C may rotate bitswithin the I subgroupings and within the Q subgroupings of the QAMsymbol-bit groupings of third spatial stream 111C by two bit positions,although the scope of the invention is not limited in this respect.

In some embodiments that transmit more than three spatial streams,multicarrier transmitter 100 may also comprise third bit-groupingshifter 112D to shift QAM symbol-bit groupings of fourth spatial stream111D by a predetermined number of subcarriers based on a spatial streamindex of fourth spatial stream 111D. Multicarrier transmitter 100 mayalso include third bit-position permuter 114D to rotate bits within theI subgroupings and within the Q subgroupings of the QAM symbol-bitgroupings of fourth spatial stream 111D by a predetermined number ofbit-positions for all of the subcarriers of the multicarriercommunication signal. The predetermined number may be based on thespatial stream index of fourth spatial stream 111D. In theseembodiments, multicarrier transmitter 100 may include symbol mapper 116Dto symbol-modulate the QAM symbol-bit groupings of fourth spatial stream115D after operations of third bit-grouping shifter 112D and thirdbit-position permuter 114D to generate a fourth plurality ofsymbol-modulated subcarriers 117D. The fourth plurality ofsymbol-modulated subcarriers 117D may comprise a fourth OFDM symbol forsubsequent transmission by fourth antenna 120D. In some of theseembodiments, third bit-grouping shifter 112D may shift each QAMsymbol-bit grouping of fourth spatial stream 111D by nine subcarriers,and third bit-position permuter 114D may rotate bits within the Isubgroupings and within the Q subgroupings of the QAM symbol-bitgroupings of fourth spatial stream 111C by three bit positions, althoughthe scope of the invention is not limited in this respect.

In some embodiments, multicarrier transmitter 100 generates amulticarrier symbol for each of the spatial streams. Each multicarriersymbol may comprise a plurality of symbol-modulated subcarriers of amulticarrier communication signal. In some embodiments, each antenna maytransmit an OFDM symbol on the same frequency subcarriers as the otherantennas. In these embodiments, antenna diversity is employed to allowthe transmission of additional data (e.g., more than one spatial stream)without an increase in frequency bandwidth.

Although multicarrier transmitter 100 is illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, processing elements may comprise one or more microprocessors,DSPs, application specific integrated circuits (ASICs), and combinationsof various hardware and logic circuitry for performing at least thefunctions described herein. In some embodiments, some functionalelements of multicarrier transmitter 100 may refer to one or moreprocesses operating on one or more processing elements.

In some embodiments, multicarrier transmitter 100 may transmit an OFDMpacket on a multicarrier communication channel. The multicarriercommunication channel may be within a predetermined frequency spectrum.The multicarrier communication channel may comprise a plurality oforthogonal subcarriers. In some embodiments, the orthogonal subcarriersof a multicarrier communication channel may be closely spaced OFDMsubcarriers. To achieve orthogonality between closely spacedsubcarriers, in some embodiments, the subcarriers of a particularmulticarrier communication channel may have a null at substantially acenter frequency of the other subcarriers of that channel.

In some embodiments, multicarrier transmitter 100 may communicate withone or more other communication stations over an OFDM communicationchannel. In some embodiments, the OFDM communication channel maycomprise one or more spatial channels associated with each subchannel.In some embodiments, spatial channels associated with a particularmulticarrier channel may overlap in frequency (i.e., use the samesubcarriers) and orthogonality may be achieved through beamformingand/or antenna diversity.

In some embodiments, the frequency spectrums for a multicarriercommunication channel may comprise either a 5 GHz frequency spectrum ora 2.4 GHz frequency spectrum, although the scope of the invention is notlimited in this respect. In these embodiments, the 5 GHz frequencyspectrum may include frequencies ranging from approximately 4.9 to 5.9GHz, and the 2.4 GHz spectrum may include frequencies ranging fromapproximately 2.3 to 2.5 GHz, although the scope of the invention is notlimited in this respect, as other frequency spectrums are equallysuitable.

In some embodiments, multicarrier transmitter 100 may be part of awireless communication device. The wireless communication device may bea personal digital assistant (PDA), a laptop or portable computer withwireless communication capability, a web tablet, a wireless telephone, awireless headset, a pager, an instant messaging device, a digitalcamera, an access point or other device that may receive and/or transmitinformation wirelessly. In some embodiments, multicarrier transmitter100 may transmit and/or receive RF communications in accordance withspecific communication standards, such as the Institute of Electricaland Electronics Engineers (IEEE) standards including IEEE 802.11(a),802.11(g/h) and/or 802.11(n) standards for wireless local area networks(WLANs) and/or 802.16 standards for wireless metropolitan area networks(WMANs), although multicarrier transmitter 100 may also be suitable totransmit and/or receive communications in accordance with othertechniques.

Each of antennas 120 may be a directional or omnidirectional antenna,including, for example, a dipole antenna, a monopole antenna, a patchantenna, a loop antenna, a microstrip antenna or other type of antennasuitable for transmission of multicarrier signals.

FIG. 6 is a flow chart of a spatial stream transmission procedure inaccordance with some embodiments of the present invention. Procedure 600may be performed by a multicarrier transmitter, such as multicarriertransmitter 100 (FIG. 1), although other multicarrier and OFDMtransmitters may also be suitable.

Operation 602 scrambles bits of an input bit stream. Operation 602 maybe performed by scrambler 102 (FIG. 1), although the scope of theinvention is not limited in this respect.

Operation 604 assigns bits of the bit stream to one of a plurality ofdata streams. Operation 604 may be performed by commutator 104 (FIG. 1),although the scope of the invention is not limited in this respect.

Operation 606 separately encodes bits of each data stream. Operation 606may be performed by encoders 106 (FIG. 1), although the scope of theinvention is not limited in this respect.

Operation 608 assigns the encoded bits in groups from the data streamsto each of a plurality of spatial streams. Operation 608 may beperformed by spatial-bit sequencer 108 (FIG. 1), although the scope ofthe invention is not limited in this respect.

Operation 610 separately performs block interleaving operations onblocks of bits of each of the spatial streams. Operation 610 may beperformed by block permuters 110A-111D (FIG. 1), although the scope ofthe invention is not limited in this respect.

Operation 612 shifts QAM bit groupings by a number of subcarriers basedon the spatial stream index associated with the spatial stream.Operation 612 may be performed by bit-grouping shifters 112B-112D(FIG. 1) for some of the spatial streams, although the scope of theinvention is not limited in this respect.

Operation 614 rotates bits among bit positions of I and Q subgroupingsof the QAM symbol-bit groupings based on the spatial stream indexassociated with the spatial stream. Operation 614 may be performed bybit-position permuters 114B-114D (FIG. 1) for some of the spatialstreams, although the scope of the invention is not limited in thisrespect.

Operation 616 maps the QAM bit groupings to QAM symbols to generate amulticarrier symbol for reach spatial stream. Operation 616 may beperformed by QAM mappers 116A-116D (FIG. 1) for each spatial stream,although the scope of the invention is not limited in this respect.

Operation 618 generates multicarrier communication signals for eachspatial stream for transmission by a corresponding antenna. Operation618 may be performed by transmit circuitry 118A-118D (FIG. 1), althoughthe scope of the invention is not limited in this respect.

Although the individual operations of procedure 600 are illustrated anddescribed as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order illustrated.

Unless specifically stated otherwise, terms such as processing,computing, calculating, determining, displaying, or the like, may referto an action and/or process of one or more processing or computingsystems or similar devices that may manipulate and transform datarepresented as physical (e.g., electronic) quantities within aprocessing system's registers and memory into other data similarlyrepresented as physical quantities within the processing system'sregisters or memories, or other such information storage, transmissionor display devices. Furthermore, as used herein, computing deviceincludes one or more processing elements coupled with computer-readablememory that may be volatile or non-volatile memory or a combinationthereof.

Embodiments of the invention may be implemented in one or a combinationof hardware, firmware and software. Embodiments of the invention mayalso be implemented as instructions stored on a machine-readable medium,which may be read and executed by at least one processor to perform theoperations described herein. A machine-readable medium may include anymechanism for storing or transmitting information in a form readable bya machine (e.g., a computer). For example, a machine-readable medium mayinclude read-only memory (ROM), random-access memory (RAM), magneticdisk storage media, optical storage media, flash-memory devices,electrical, optical, acoustical or other form of propagated signals(e.g., carrier waves, infrared signals, digital signals, etc.), andothers.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims.

In the foregoing detailed description, various features are occasionallygrouped together in a single embodiment for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments of the subjectmatter require more features than are expressly recited in each claim.Rather, as the following claims reflect, invention may lie in less thanall features of a single disclosed embodiment. Thus the following claimsare hereby incorporated into the detailed description, with each claimstanding on its own as a separate preferred embodiment.

1. A multicarrier transmitter for transmitting at least first and secondspatial streams comprising: a bit-grouping shifter to shift symbol-bitgroupings of the second spatial stream among subcarriers of amulticarrier communication signal; and a bit-position permuter to rotatebits among bit positions within subgroupings of the symbol-bit groupingsof the second spatial stream.
 2. The transmitter of claim 1 wherein thesymbol-bit groupings are quadrature-amplitude-modulation (QAM) bitgroupings, and wherein the subgroupings comprise in-phase (I)subgroupings and quadrature-phase (Q) subgroupings, and wherein thebit-position permuter is adapted to circularly rotate bits amongpositions within the I subgroupings and within the Q subgroupings. 3.The transmitter of claim 2 wherein the QAM bit groupings having apredetermined number of bits associated therewith, wherein thepredetermined number of bits per QAM bit grouping ranges from two bitsper symbol to eight bits per symbol.
 4. The transmitter of claim 1further comprising: a first symbol modulator to symbol-modulatesymbol-bit groupings of the first spatial stream to generate a firstplurality of symbol-modulated subcarriers; and a second symbol modulatorto symbol-modulate the symbol-bit groupings of the second spatial streamafter operation of the bit-grouping shifter and the bit-positionpermuter to generate a second plurality of symbol-modulated subcarriers.5. The transmitter of claim 4 wherein the first plurality ofsymbol-modulated subcarriers comprise a first orthogonal frequencydivision multiplexed symbol for subsequent transmission by a firstantenna, and wherein the second plurality of symbol-modulatedsubcarriers comprises a second orthogonal frequency division multiplexedsymbol for subsequent transmission by a second antenna.
 6. Thetransmitter of claim 4 further comprising: a first block permuter toperform a block interleaving operation on bits associated with the firstspatial stream; and a second block permuter to perform the blockinterleaving operation on bits associated with the second spatial streamprior operation of the bit-grouping shifter and the bit-positionpermuter.
 7. The transmitter of claim 5 wherein the bit-grouping shifteris a first bit-grouping shifter and the bit-position permuter is a firstbit-position permuter, wherein the first bit-grouping shifter is adaptedto shift each symbol-bit grouping of the second spatial stream by apredetermined number of subcarriers based on a spatial stream index ofthe second spatial stream, and wherein the first bit-position permuteris adapted to rotate bits within the subgroupings of the symbol-bitgroupings of the second spatial stream by a predetermined number of bitpositions for all of the subcarriers of the multicarrier communicationsignal, the predetermined number bit positions based on the spatialstream index of the second spatial stream.
 8. The transmitter of claim 4wherein each spatial stream is to be transmitted by one of a pluralityof a transmit antennas.
 9. The transmitter of claim 4 furthercomprising: a commutator to assign bits of a bit stream to one of aplurality of data streams; and a spatial-bit sequencer to select groupsof bits from each of the data streams to generate the at least first andsecond spatial streams.
 10. The transmitter of claim 9 furthercomprising: an encoder associated with each data stream to receive theassigned bits from the commutator and to perform an encoding operationon the assigned bits, block permuters associated with each of thespatial streams to perform a block interleaving operation on bitsprovided by the spatial-bit sequencer.
 11. The transmitter of claim 2wherein the bit-position permuter circularly rotates bits amongbit-positions within each of a plurality QAM bit groupings, wherein eachof the QAM bit groupings is associated with one subcarrier of themulticarrier communication signal, wherein the bit-grouping shiftershifts QAM bit groupings by a plurality of subcarriers of themulticarrier communication signal.
 12. The transmitter of claim 1wherein the transmitter generates a multicarrier symbol for each of thespatial streams, each multicarrier symbol comprising a plurality ofsymbol-modulated subcarriers of the multicarrier communication signal.13. The transmitter of claim 12 wherein the multicarrier communicationsignal is an orthogonal frequency division multiplexed signal, andwherein the symbol-modulated subcarriers have a null at substantially acenter frequency of the other subcarriers to achieve orthogonalitytherebetween.
 14. A multicarrier transmitter comprising: bit-groupingshifters to shift symbol-bit groupings among subcarriers of at least onespatial stream of a plurality of spatial streams; and bit-positionpermuters to rotate bits among bit positions within subgroupings of thesymbol-bit groupings of the at least one spatial stream.
 15. Thetransmitter of claim 14 wherein the bit-grouping shifters and thebit-position permuters are associated with less than all of the spatialstreams of the plurality, wherein each spatial stream has a spatialstream index associated therewith, wherein the bit-grouping shifter isadapted to shift the symbol-bit groupings by a predetermined number ofsubcarriers based on the associated spatial stream index, and whereinthe bit-position permuter is adapted to rotate bits within subgroupingsof the symbol-bit groupings by a predetermined number of bit positionsfor all subcarriers based on the associated spatial stream index. 16.The transmitter of claim 15 further comprising symbol modulators tosymbol modulate the symbol-bit groupings of each of the spatial streamsto generate a corresponding plurality of symbol-modulated subcarriersfor subsequent transmission on a corresponding antenna, wherein eachplurality of symbol-modulated subcarriers comprises an orthogonalfrequency division multiplexed symbol.
 17. The transmitter of claim 16further comprising: block interleavers associated with each spatialstream to perform a block interleaving operation on each spatial stream,the block interleavers to operate in a signal path prior to operation ofthe bit-grouping shifters and operation of the bit-position permuters onless than all of the spatial streams; a commutator to assign bits of abit stream to one of a plurality of data streams; a spatial-bitsequencer to select groups of bits from each of the data streams togenerate the plurality of spatial streams to provide to an associatedone of the block interleavers; and an encoder associated with each ofthe data streams to separately encode bits of each of the data streamsto generate encoded data streams, wherein the spatial-bit sequencer isadapted to select bits from each of the encoded data streams to generatethe spatial streams.
 18. A method for transmitting two or more spatialstreams comprising: shifting symbol-bit groupings among subcarriers ofat least one spatial stream; and rotating bits among bit positionswithin subgroupings of the symbol-bit groupings of the at least onespatial stream.
 19. The method of claim 18 wherein the shifting thesymbol-bit groupings and the rotating bits among the bit positions areperformed for less than all of a plurality of the spatial streams. 20.The method of claim 19 wherein each spatial stream has a spatial streamindex associated therewith, wherein the symbol-bit groupings are shiftedby a predetermined number of subcarriers based on the associated spatialstream index, and wherein bits are rotated within subgroupings of thesymbol-bit groupings by a predetermined number of bit positions for allsubcarriers based on the associated spatial stream index.
 21. The methodof claim 20 wherein the symbol-bit groupings arequadrature-amplitude-modulation (QAM) bit groupings, and wherein thesubgroupings comprise in-phase (I) subgroupings and quadrature-phase (Q)subgroupings, wherein the bits are circularly rotated among positionswithin the I subgroupings and within the Q subgroupings.
 22. The methodof claim 20 further comprising symbol modulating the symbol-bitgroupings of each of the spatial streams to generate a correspondingplurality of symbol-modulated subcarriers for subsequent transmission ona corresponding antenna, wherein each plurality of symbol-modulatedsubcarriers comprises an orthogonal frequency division multiplexedsymbol.
 23. The method of claim 22 wherein each plurality of subcarrierscomprises a plurality of substantially orthogonal subcarriers of amulticarrier communication signal.
 24. The method of claim 22 furthercomprising performing a block interleaving operation on each spatialstream prior to shifting the symbol-bit groupings and rotating bitsamong the bit positions on less than all of the spatial streams.
 25. Themethod of claim 24 further comprising: assigning bits of a bit stream toone of a plurality of data streams; selecting groups of bits from eachof the data streams to generate the plurality of spatial streams. 26.The method of claim 25 further comprising separately encoding bits ofeach of the data streams to generate encoded data streams, whereinselecting comprising selecting bits from each of the encoded datastreams.
 27. A system comprising: two or more substantiallyomnidirectional antennas; bit-grouping shifters to shift symbol-bitgroupings among subcarriers of at least one spatial stream of aplurality of spatial streams; and bit-position permuters to rotate bitsamong bit positions within subgroupings of the symbol-bit groupings ofthe at least one spatial stream for subsequent transmission by theantennas.
 28. The system of claim 27 wherein the bit-grouping shiftersand the bit-position permuters are associated with less than all of thespatial streams of the plurality, wherein each spatial stream has aspatial stream index associated therewith, wherein the bit-groupingshifter is adapted to shift the symbol-bit groupings by a predeterminednumber of subcarriers based on the associated spatial stream index, andwherein the bit-position permuter is adapted to rotate bits withinsubgroupings of the symbol-bit groupings by a predetermined number ofbit positions for all subcarriers based on the associated spatial streamindex.
 29. The system of claim 28 further comprising symbol modulatorsto symbol modulate the symbol-bit groupings of each of the spatialstreams to generate a corresponding plurality of symbol-modulatedsubcarriers for subsequent transmission on a corresponding antenna,wherein each plurality of symbol-modulated subcarriers comprises anorthogonal frequency division multiplexed symbol.
 30. The system ofclaim 29 further comprising: block interleavers associated with eachspatial stream to perform a block interleaving operation on each spatialstream, the block interleavers to operate in a signal path prior tooperation of the bit-grouping shifters and operation of the bit-positionpermuters on less than all of the spatial streams; a commutator toassign bits of a bit stream to one of a plurality of data streams; aspatial-bit sequencer to select groups of bits from each of the datastreams to generate the plurality of spatial streams to provide to anassociated one of the block interleavers; and an encoder associated witheach of the data streams to separately encode bits of each of the datastreams to generate encoded data streams, wherein the spatial-bitsequencer is adapted to select bits from each of the encoded datastreams to generate the spatial streams.
 31. A machine-readable mediumthat provides instructions, which when executed by one or moreprocessors, cause the processors to perform operations for transmittingtwo or more spatial streams comprising: shifting symbol-bit groupingsamong subcarriers of at least one spatial stream; and rotating bitsamong bit positions within subgroupings of the symbol-bit groupings ofthe at least one spatial stream.
 32. The machine-readable medium ofclaim 31 wherein the instructions, when further executed by one or moreof the processors cause the processors to perform operations wherein theshifting the symbol-bit groupings and the rotating bits among the bitpositions are performed for less than all of a plurality of the spatialstreams.
 33. The machine-readable medium of claim 32 wherein theinstructions, when further executed by one or more of the processorscause the processors to perform operations wherein each spatial streamhas a spatial stream index associated therewith, wherein the symbol-bitgroupings are shifted by a predetermined number of subcarriers based onthe associated spatial stream index, and wherein bits are rotated withinsubgroupings of the symbol-bit groupings by a predetermined number ofbit positions for all subcarriers based on the associated spatial streamindex.